Many authors overuse words involving looking and eyes. They describe their characters looking, glancing, gazing, staring, studying, seeing, surveying, scanning, peeking, leering, ogling, noticing, watching, blinking, glaring, and just generally eyeballing everything. Characters' eyes flash, burn, linger, darken or brighten, and even change color. Characters' eyes drop to the floor (ouch!); they roam around the room (eeek!). Or characters may raise the ever-popular eyebrow.
At Bantam Doubleday Dell, I once edited a book in which the author described characters looking in almost every paragraph. The author gave his male character a line of dialogue, then said, "He looked at her." Then the female character said a line of dialogue, and "her eyes narrowed on him." Then the male character spoke, and "he looked away." The female character said nothing, only "stared at him." This went on for 600 pages.
While that is an extreme example, overuse of looking/eye words is a problem for many writers today. They visualize their stories as movies. In movies, looks exchanged between two actors can be very revealing. Their expressions reveal nuances of the characters and their relationships quite skillfully. Unfortunately, looks exchanged between two characters in a book are not revealing. An author may write, "He looked at her," and see those expressions in his head, fascinating and filled with nuance. But the reader doesn't see this. The reader just sees one character looking at the other.
These terms also carry other problems. If an author describes eyes as burning or flashing, these are clichˇs and don't reflect reality. In reality, eyes remain relatively unchanged, except for pupil size. It's the skin and face around the eyes that control a person's expression.
Eyes that are "filled with conviction" or "shadowed with longing" are weak shortcuts telling us what the character is feeling. It would almost always be better to show us what the character is feeling.
So search your manuscripts and see how many eyeballs are roaming your pages. Come up with other ways of revealing the thoughts or emotions of the characters besides describing their eyes. Small actions or gestures can be extremely revealing and powerful. Most authors could strengthen their work by cutting at least 50% of these looking/eye words. Sometimes a description of a gaze or a glance can be amazingly significant. But if your characters are gazing in every paragraph, then it won't mean much.